Efficiency in a fluidized catalytic cracking (FCC) apparatus is dependent on a number of factors. One important factor is the energy used to atomize the liquid hydrocarbon feed introduced into the FCC reactor.
In general, the liquid hydrocarbon feed is atomized by a gas such as steam for discharge through a nozzle into the FCC reactor. The amount of steam used to atomize the liquid hydrocarbon feed impacts directly on the efficiency of the reaction. The shape and number of slots in the nozzle have also been found to impact directly on the atomization of the liquid hydrocarbon feed.
Additionally, it is well known that the FCC reaction yields improved results when the fluidized feed introduced into the reactor has a large surface area. In this regard, the smaller the size of the droplets, or the finer the spray from the nozzle, the larger the surface area of the fluidized feed. Creating a fine spray of the hydrocarbon feed from the nozzle using less steam results in greater efficiency of the fluidized catalytic cracking system.
Earlier nozzles used to atomize the fluid hydrocarbon feed had a generally hemispherical discharge end formed with a single elongated slot-like orifice adapted to produce a flat fan-like spray. An example of such a nozzle is described in U.S. Pat. No. 5,306,418 to Dou et al.
Later nozzles utilized two elongated orifices to atomize the fluid hydrocarbon feed. As described in U.S. Pat. No. 5,673,859 to Haruch, the use of a plurality of slot-like outlets atomize the liquid feed into finer particles as the liquid is discharged from the nozzle. U.S. Pat. No. 5,673,859 further described that the use of slots angled relative to one another produce a converging spray, further improving post-discharge atomization of the liquid particles.
However, an FCC hydrocarbon liquid feed nozzle having a plurality of slots is prone to failure over time. The reactor in which the nozzle operates has constantly moving fluidized catalyst particles circulating throughout the reactor. The nozzles are therefore acted upon not only by the hydrocarbon feed passing through the nozzles, but also by the fluidized catalyst. Due to the flow patterns around the nozzle when the liquid hydrocarbon feed is being sprayed into the reactor, the area between the slots is subject to severe erosion of the inter-slot wall.
It is therefore an object of the present invention to provide an improved hydrocarbon feed nozzle, resulting in more efficient atomization of the hydrocarbon feed over a longer useful life.